1. Field of the Invention
This invention relates to a key switch apparatus for use in electronic musical instruments having a structure in which multi-stage bus bars are allowed to contact multiple terminal strips by a key-driven actuator so as to produce multiple tones simultaneously.
2. Description of the Prior Art
Some electronic musical instruments equipped with a key switch apparatus that is turned on and off by key operation have bus bars vertically tensioned in multiple stages to produce multiple tones, such as 16xe2x80x2, 8xe2x80x2, 4xe2x80x2, 22/3xe2x80x2 and 2xe2x80x2, simultaneously. Bus bars are installed under the keys, extending from the bottom bass key to the top treble key. On the side of the actuator moved by key operation, there are terminal strips that will contact the bus bars. These terminal strips are pushed onto the bus bars almost simultaneously by key depression to provide signal current. Such a key mechanism tends to be too high, and electronic musical instruments equipped with this mechanism tend to be bulky. The mechanism also has the disadvantage of being too thick to be installed in a flat one-stage keyboard. In addition, due to the huge number of switch circuits, wiring work is time-consuming and lowers productivity.
This invention has been made to solve the above problems, and its object is therefore to downsize the key switch apparatus, particularly its height, and to provide a key switch apparatus sufficiently compact to be adopted in keyboard-type electronic musical instruments. The other object of the present invention is to eliminate complex wiring work by, for example, forming the key switch mechanism into a single unit for each key so as to improve productivity.
The above and other objects have been attained by installing multiple bus bars with intervals in each stage, multiple terminal strips that can contact the bus bars individually in each stage, and a terminal-strip engaging means for controlling the movements of the terminal strips in the actuator. Further, this invention also can provide a key switch apparatus for electronic musical instruments characterized in that the apparatus has: a mounting frame having multiple through-holes for bus bars in each stage and being installed under each key; an actuator having engaging windows through which multiple terminal strips penetrate and being installed so that it can move vertically in the mounting frame and can reach a key at the top of the frame; and a printed circuit board that has terminals for connection to the ends of the multiple terminal strips; and an electric circuit that obtains signal current corresponding to multiple tones to be produced simultaneously.
The key switch apparatus set forth in this invention is to be employed in electronic musical instruments, specifically electronic keyboard musical instruments, and, in principle, this apparatus has a structure in which multi-stage bus bars are allowed to contact multiple terminal strips by a key-driven actuator so as to produce multiple tones simultaneously.
For example, a conventional electronic organ may have ten bus bars arrayed in ladder form, each having a corresponding terminal strip wired to a circuit. Then, such bus bars occupy significant installation space, and a large number of wires, approximately 2000 in this case, must be handled for electric connection. Conventionally, ten bus bars are arrayed individually in ten stages, so that each terminal strip contacts the corresponding bus bar. This conventional basic structure is regarded in the invention as a technological problem.
In the present invention, multiple bus bars are shifted in location in each stage. If more than one bus bar can be installed in each stage, the necessary number of stages decreases accordingly to a fraction of the number of bus bars installed in each stage. For example, ten stages of bus bars (one bus bar each) can be decreased by half, to five stages, if each stage has two bus bars. The locations of bus bars may be shifted in any direction, according to their configuration for installation. For example, the bus bars tensioned along laterally-arranged natural keys should be shifted ahead and behind in location. In addition, they may be shifted vertically at the same time.
Multiple terminal strips are installed in each stage so that they will contact the individual bus bars. Each terminal strip is located so as to contact each of the bus bars shifted in location in each stage. For example, when multi-stage bus bars are shifted in location ahead and behind in each stage, the corresponding multiple terminal strips are installed, with their locations shifted laterally, in each stage.
An engaging mechanism for contact with terminal strips is installed in an actuator so as to control the key-driven movement of the terminal strips. The actuator may be of any type, provided that it moves in accordance with key depression to move and contact the terminal strips with bus bars. The actuator of the invention, however, has an engaging means for controlling the movement of the multiple terminal strips. By virtue of this mechanism, the distances between the individual bus bars and corresponding terminal strips become almost equal, and it thereby allows the terminal strips to contact the bus bars that have been shifted to predetermined positions almost simultaneously. This effect is obtained, for example, by providing a difference in height in the area where the actuator contacts the terminal strips.
In such a key switch apparatus for electronic musical instruments, its mounting frame may have through-holes for bus bars and an installation space for the actuator. This mounting frame limits the locations of bus bars and the movement of the actuator against the bus bars, so that the terminal strips may contact the bus bars almost simultaneously. The ends of the multiple terminal strips may be connected to a printed circuit board. The printed circuit board has a circuit, for example, that obtains signal current corresponding to multiple tones that will be produced simultaneously. Then, because wiring is completed simply by coupling the printed circuit board with the mounting frame, the key switch apparatus can be made into a single unit for each key, and thereby its structure can be significantly simplified. If the key switch unit module is made equal to or smaller than the width of a key, it becomes sufficiently compact to be installed beneath each key.